Department of Biochemistry and Molecular Biology, Mississippi State University, Mississippi State, Mississippi, United States of America.
PLoS Genet. 2013;9(3):e1003322. doi: 10.1371/journal.pgen.1003322. Epub 2013 Mar 7.
Cereal endosperm represents 60% of the calories consumed by human beings worldwide. In addition, cereals also serve as the primary feedstock for livestock. However, the regulatory mechanism of cereal endosperm and seed development is largely unknown. Polycomb complex has been shown to play a key role in the regulation of endosperm development in Arabidopsis, but its role in cereal endosperm development remains obscure. Additionally, the enzyme activities of the polycomb complexes have not been demonstrated in plants. Here we purified the rice OsFIE2-polycomb complex using tandem affinity purification and demonstrated its specific H3 methyltransferase activity. We found that the OsFIE2 gene product was responsible for H3K27me3 production specifically in vivo. Genetic studies showed that a reduction of OsFIE2 expression led to smaller seeds, partially filled seeds, and partial loss of seed dormancy. Gene expression and proteomics analyses found that the starch synthesis rate limiting step enzyme and multiple storage proteins are down-regulated in OsFIE2 reduction lines. Genome wide ChIP-Seq data analysis shows that H3K27me3 is associated with many genes in the young seeds. The H3K27me3 modification and gene expression in a key helix-loop-helix transcription factor is shown to be regulated by OsFIE2. Our results suggest that OsFIE2-polycomb complex positively regulates rice endosperm development and grain filling via a mechanism highly different from that in Arabidopsis.
谷物胚乳占全世界人类消耗卡路里的 60%。此外，谷物也是牲畜的主要饲料来源。然而，谷物胚乳和种子发育的调控机制在很大程度上尚不清楚。多梳复合物已被证明在拟南芥胚乳发育的调控中发挥关键作用，但它在谷物胚乳发育中的作用仍不清楚。此外，多梳复合物的酶活性在植物中尚未得到证明。在这里，我们使用串联亲和纯化纯化了水稻 OsFIE2-多梳复合物，并证明了其特定的 H3 甲基转移酶活性。我们发现 OsFIE2 基因产物负责体内特异性产生 H3K27me3。遗传研究表明，OsFIE2 表达减少导致种子变小、部分饱满和部分丧失休眠。基因表达和蛋白质组学分析发现，OsFIE2 减少系中淀粉合成限速酶和多种贮藏蛋白下调。全基因组 ChIP-Seq 数据分析表明，H3K27me3 与幼种子中的许多基因有关。H3K27me3 修饰和关键螺旋-环-螺旋转录因子的基因表达受 OsFIE2 调控。我们的研究结果表明，OsFIE2-多梳复合物通过一种与拟南芥高度不同的机制正向调控水稻胚乳发育和灌浆。
